The field of this invention is pedestal crane bearing systems, particularly of the type providing bearing surfaces between the upperworks of the pedestal crane assembly and the pedestal.
Prior art crane bearing systems typically require the use of large, machined shear ball bearings mounted on or adjacent to the upper perimeter of the pedestal. These shear ball bearings provide for rotation of the upperworks about the pedestal as well as support the upperworks against all stresses and strains encountered due to loading on the crane boom. Typically, such shear ball bearings are difficult to replace requiring additional heavy duty machinery for removing the pedestal crane assembly from the pedestal itself to allow access to the worn or damaged bearing components.
Prior art devices include those bearing structures disclosed in U.S. Pat. Nos. 46,213; 884,666; 2,414,573; 2,825,471; 3,148,778; 3,258,130; and, West German Patent Nos. 1,195,918 and 2,025,169. All such references disclose various bearing arrangements; however, none address the specific problem or difficulties encountered in the removal and maintenance of such bearings located adjacent to the upper end of the pedestal or those located about the exterior perimeter of the pedestal. U.S. Pat. No. 4,061,230 to the inventors of the instant invention, while recognizing the problem, provides different bearing structure for supporting the pedestal crane assembly about the support column of the pedestal. However, this reference does not contemplate nor teach a unitary structure or method for permitting ease of access to such bearings for inspection or removal.